[PATCH] D56821: [CodeGen] Always use string computed in Sema for PredefinedExpr

[Eli Friedman via Phabricator via cfe-commits]

efriedma created this revision.
efriedma added reviewers: rjmccall, rsmith.

We can't use any other string, anyway, because its type wouldn't match the type of the PredefinedExpr.

With this change, we don't compute a "nice" name for the __func__ global when it's used in the initializer for a constant. This doesn't seem like a great loss, so I'm not sure it's worth fixing.  We would either need to store more information in the AST, or somehow make constant evaluation keep track of the parent function of the PredefinedExpr.

This could change behavior in some situations involving BlockDecl. Currently, CodeGenFunction::EmitPredefinedLValue has some logic to intentionally emit a string different from what Sema computed.  Specifically, it does two things: one, it appends numbers to the string if there are multiple block expressions in the function that use __func__, and two, it rewrites __func__ for blocks in the initializer for a global variable. This code skips that logic... but changing the string in CodeGen is fundamentally broken anyway.  (For example, sizeof(__func__) returns the wrong result.) Hopefully this doesn't affect practical code.

Fixes https://bugs.llvm.org/show_bug.cgi?id=40313 .


Repository:
  rC Clang

https://reviews.llvm.org/D56821

Files:
  lib/CodeGen/CGExprConstant.cpp
  test/CodeGen/const-init.c
  test/CodeGenCXX/predefined-expr-cxx14.cpp


Index: test/CodeGenCXX/predefined-expr-cxx14.cpp
===================================================================
--- test/CodeGenCXX/predefined-expr-cxx14.cpp
+++ test/CodeGenCXX/predefined-expr-cxx14.cpp
@@ -20,6 +20,8 @@
 // CHECK-DAG: @__func__.___ZN16ClassBlockConstrD2Ev_block_invoke = private unnamed_addr constant [31 x i8] c"~ClassBlockConstr_block_invoke\00"
 // CHECK-DAG: @__func__.___ZN16ClassBlockConstrC2Ev_block_invoke = private unnamed_addr constant [30 x i8] c"ClassBlockConstr_block_invoke\00"
 
+// CHECK-DAG: private unnamed_addr constant [32 x i8] c"const char *ConstexprPrettyFn()\00"
+
 int printf(const char * _Format, ...);
 
 class ClassInTopLevelNamespace {
@@ -83,6 +85,11 @@
   const char *getFunc() const { return Func; }
 };
 
+constexpr const char* ConstexprPrettyFn() {
+  return __PRETTY_FUNCTION__;
+}
+const char* ConstexprPrettyVar = ConstexprPrettyFn();
+
 int
 main() {
   int a;
Index: test/CodeGen/const-init.c
===================================================================
--- test/CodeGen/const-init.c
+++ test/CodeGen/const-init.c
@@ -121,8 +121,8 @@
 struct g23 {char a; short b; char c; struct g22 d;};
 struct g23 g24 = {1,2,3,4};
 
-// CHECK: @g25.g26 = internal global i8* getelementptr inbounds ([4 x i8], [4 x i8]* @__func__.g25, i32 0, i32 0)
-// CHECK: @__func__.g25 = private unnamed_addr constant [4 x i8] c"g25\00"
+// CHECK: @g25.g26 = internal global i8* getelementptr inbounds ([4 x i8], [4 x i8]* @[[FUNC:.*]], i32 0, i32 0)
+// CHECK: @[[FUNC]] = private unnamed_addr constant [4 x i8] c"g25\00"
 int g25() {
   static const char *g26 = __func__;
   return *g26;
@@ -153,7 +153,7 @@
       DCC_PASSWD passwd;
   } DCC_SRVR_NM;
   // CHECK: @g29.a = internal global %struct.DCC_SRVR_NM { [2 x i8] c"@\00" }, align 1
-  // CHECK: @g29.b = internal global [1 x i32] [i32 ptrtoint ([5 x i8]* @.str to i32)], align 4
+  // CHECK: @g29.b = internal global [1 x i32] [i32 ptrtoint ([5 x i8]* @.str.1 to i32)], align 4
   // CHECK: @g29.c = internal global [1 x i32] [i32 97], align 4
   static DCC_SRVR_NM a = { {"@"} };
   static int b[1] = { "asdf" }; // expected-warning {{incompatible pointer to integer conversion initializing 'int' with an expression of type 'char [5]'}}
Index: lib/CodeGen/CGExprConstant.cpp
===================================================================
--- lib/CodeGen/CGExprConstant.cpp
+++ lib/CodeGen/CGExprConstant.cpp
@@ -1789,17 +1789,7 @@
 
 ConstantLValue
 ConstantLValueEmitter::VisitPredefinedExpr(const PredefinedExpr *E) {
-  if (auto CGF = Emitter.CGF) {
-    LValue Res = CGF->EmitPredefinedLValue(E);
-    return cast<ConstantAddress>(Res.getAddress());
-  }
-
-  auto kind = E->getIdentKind();
-  if (kind == PredefinedExpr::PrettyFunction) {
-    return CGM.GetAddrOfConstantCString("top level", ".tmp");
-  }
-
-  return CGM.GetAddrOfConstantCString("", ".tmp");
+  return CGM.GetAddrOfConstantStringFromLiteral(E->getFunctionName());
 }
 
 ConstantLValue


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